A new sensitive method for determining endotoxin in whole blood.

We developed a microplate method for determining endotoxin in whole blood with Endospecy, an endotoxin-specific chromogenic limulus test reagent. The factors in blood that would interfere with the test were successfully removed by exposing samples to 0.66 mol/l HNO3 containing 0.25% Triton X-100. Recoveries of various endotoxins spiked into whole blood of humans and experimental animals were almost complete, and were not enhanced by sample dilution. Normal endotoxin concentration in human whole blood was less than 10 pg/ml in reference to Escherichia coli 0111:B4 endotoxin. Measurements on paired whole blood and platelet-rich plasma (PRP) samples from 50 normal and 132 diseased subjects showed a good correlation (r = 0.901, P less than 0.01). This microplate whole blood method has advantages over the conventional PRP method in that it requires less time, less amount of sample and limulus reagent, and less risk of contamination during the procedure.